Doesn’t matter how good your indoor climate is, you still need to spend more time outside
There is an ongoing discussion about the optimal indoor environment in buildings to foster the health, well-being, and productivity of humans. This concerns most of us, either we are office workers, students, or school kids (or parents of school kids). When talking about indoor environment, the factors often researched are indoor temperature, light conditions, and indoor air quality, including the concentration of carbon dioxide and fine particles in a room.
Light is of particular importance because it is still difficult to replicate the light conditions, a human is exposed outside under sunlight. While some manufactures claim to have special lamps and light systems in their product portfolio that replicates the sunlight, due to its fixed position, it cannot replicate the movement of the sun over the day. But does that really matter? Isn’t it enough to have a sufficiently bright light in a room to prevent adverse effects on human health? What are the possible negative effects of artificial light?
Sunlight is of particular importance for human health for several factors. The first one is that we need sunlight to set our inner clock correctly, called the circadian rhythm. The eyes are the only way the brain receives information about the time of day. The body needs to know if it is early or late in the day to calibrate hormonal processes which are important to function well. For example, sunlight exposure of between 10 and 30 minutes early in the morning will set the cycle for cortisol production, a hormone well knows as the stress hormone. However, what is often disregarded is that having a constantly low cortisol level does not mean we get rid of the stress. We want to have a variance in the cortisol level, because we need a peak in its production in the morning to feel awake, and a drop in the evening to better fall asleep. Being exposed to sunlight in the morning sets the cortisol level correctly, which aligns the inner clock with the actual daytime. This is of crucial importance to have good sleep, and good sleep is key to being productive, balanced, and dealing with a stressful job.
Secondly, sunlight is important for eye health and vision. Myopia or short sightseeing is regarded as a global pandemic; the growth rate of children and adults developing myopia is increasing for decades now. However, it was believed that reading, working in front of a screen, or in general looking most of the time at objects in a short distance is the main cause for myopia. This is partly true because the muscles around the eyeball relax when we focus on positions in the far, and contract when we look at objects nearby. Thus, looking constantly at objects in close proximity means you constantly contract your muscles, therefore they become tight and cannot fully relax after a while.
However, the newest research showed that sunlight is of even greater importance to keep vision healthy and avoid myopia. A recent study investigated this relationship. The time children spent outside was increased, including also shifting the classroom to outside. The study showed that for these children, even that they read as usual and thus engaged in close-distance focusing, because they did so outside under sunlight, the odds for this group to develop myopia decreased by over 50%. Other studies support this finding, concluding that sunlight is important for the development of good vision in children and the maintaining of it during adulthood.
Now, some people would argue that these effects are probably due to the light intensity of the sun, thus it could be easily simulated by artificial light. This is only part of the full story. What is also important information for the body is the position of the light source and the light color. Starting with light color, most people have probably heard of the negative effect of blue light from screens, causing a disturbance in sleep. Many, including companies, concluded from that that the blue light spectrum of a light source is in general bad, thus companies offer blue light filters for screens, apps to reduce blue light, or blue light blocking glasses. Exposure to blue light in the evening is indeed one of the main factors contributing to problems falling asleep and staying asleep. However, the body needs to be exposed to blue light during the day. This is needed for the brain to receive correct information about the daytime, thus aligning hormonal and other processes in the body, which contribute to well-being, wakefulness, and productivity. So yes, avoiding blue light during evening hours is good, but getting enough sunlight including the blue light spectrum during the day is of equal importance.
Additionally, the eye has a higher density of receptors in the lower part, which makes it feasible for the brain to detect the position of the light source. This is the way the brain know if it is early in the day (light source is low, shining more to the lateral side of the eye, plus the amount of blue light is lower), or in the middle of the day (light comes from the top, blue light share is highest).
To conclude, what are the implications of these findings? First, if companies want to offer products that simulate sunlight and thus foster the health of humans, they have to take into account the brightness, color, and position of the light source, and keep it dynamically changing over the day. Secondly, if you want to optimize your eye health, but also your general well-being and productivity, there is no way around spending more time of your day outside.